A continuing goal of semiconductor processing is to increase integration density. This goal of increasing circuit density permeates through fabrication of all types of circuitry, including memory, logic and sensors. Significant improvement in integrated circuit density may be achieved by reducing the size of individual structures in layouts in which there is a large number of repeating units, such as with integrated memory. The individual structures of integrated memory may be comprised by memory-storage units. Example memory-storage units are NAND unit cells, dynamic random access (DRAM) unit cells, and cross-point memory unit cells.
Photolithography is a conventional method utilized for fabrication of integrated components. Photolithography utilizes light to pattern a photosensitive material. The photolithographically-patterned photosensitive material may then be utilized as a mask for patterning underlying materials to form integrated circuit components.
If only photolithography is utilized to pattern integrated circuit components, integrated circuit density cannot increase beyond a threshold dictated by the minimum attainable feature size obtainable utilizing the photolithography. The minimum feature size may be dictated by, for example, a wavelength utilized during the photolithography.
Several methods have been developed which can be utilized in combination with photolithography to push the minimum attainable feature size to smaller dimensions than may be achieved with photolithography alone. Among such methods is a procedure comprising utilization of a block copolymer to form a pattern within photolithographically-patterned features. The pattern created with the block copolymer may be at higher density than is achievable with photolithographic patterning, and thus may be utilized to create higher integrated circuit densities than are achievable with photolithography alone.
Although the utilization of block copolymers shows promise for increasing integrated circuit density, there are technical obstacles to overcome before block copolymers are adopted for wide-scale use in semiconductor device fabrication.
It would be desirable to develop new methods of forming patterns with block copolymers which enable repeating patterns to be formed to high density. It would be further desirable for such methods to be readily applicable for semiconductor device fabrication.